Transfer machine



April 15, 1969 E. w. BRIDGE TRANSFER MACHINE Sheet Filed March 30, 1967 April 15, 1969 w, BRIDGE 3,438,478

TRANSFER MACHINE Filed March so, 1967 Sheet 2 of a FIG. 2.

BY MMW April 15, 1969 E. w. BRIDGE TRANSFER MACHINE Sheet Filed March 30, 1967 April 1969 E. w. BRIDGE 3,438,478

TRANSFER MACHINE Filed March so. 1967 Sheet 5 of s April 5, 1969 E. w. BRIDGE 3,438,478

TRANSFER MACHINE Filed March :50, 1567 Sheet Q of a FIG. 7 M

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TRAN SFER MACHINE Filed March 30, 1967 Sheet 8 of 8 United States Patent U.S. Cl. 198-19 9 Claims ABSTRACT OF THE DISCLOSURE Transfer machine having a base structure providing a plurality of successive work stations and a plurality of bed segments defining a closed path past all the work stations. Each segment spans a whole number of work stations, and each has a platen-supporting surface on which slide a plurality of interconnected work-carrying platens which occupy the full extent of the closed path. A single indexing mechanism on one of the bed segments indexes all the platens simultaneously, and at least each bed segment which is associated with a tool head has a platen locating device for locating each platen individually in relation to a tool head. Shallow pockets in the platensupporting surface of each bed segment are fed with air under pressure to reduce friction between the platens and the bed segments during an indexing period.

This invention relates to machine tools of the kind commonly known in the art as transfer machines in which Work pieces are held in fixtures which are transferred to successive machining stations.

Transfer machines as hitherto constructed have either been of the in-line type in which the work is transferred in a straight line from one machining station to the next, or of the rotary type in which a solid bed or work table is indexed rotationally on a base structure about a central vertical axis, the tool heads being mounted either on a common central column or on pedestals around the outer periphery. The former type of machine occupies a considerable amount of space and there are problems of accurate levelling and alignment of a long bed and a number of tool head carrying columns or plinths. The latter type of machine is more compact but the solid rotary work table must be carried on highly accurate and hence costly bearings. Moreover, access to mechanism within the bed structure is difficult without removal of the table, requiring heavy lifting tackle and usually also the preliminary dismantling of tool heads and their central column o peripheral pedestals. Furthermore, since the table is rigid, circumferential errors in work location tend to become cumulative at successive work stations.

It is an object of the present invention to provide a transfer machine in which any work-holding fixture can be located to suit the machining station with a high degree of accuracy and without interfering with the accurate positioning of any other fixture. Another object is to provide a machine construction in which all the working parts, including the indexing mechanism, are readily accessible for maintenance and servicing without extensive dismantling.

A transfer machine in accordance with the present invention has a rigid bed forming a closed continuous path for the work and consisting of a base structure carrying a numbe of removable bed segments. On the top face of the bed is a closed loop guide track, and a number of work-carrying platens are slidable 0n the bed, each platen having guide elements cooperating with the guide track. Indexing means positions all the platens simultane- 3,438,478 Patented Apr. 15, 1969 ice ously at successive machining stations, and means is provided for accurately locating the platens with respect thereto. The platens are flexibly interconnected to form a continuous table for the work.

Preferably, the guide track is a slot or groove, and the guide elements are preferably rollers which run in the guide track, and at least one is advantageously adapted to cooperate with an indexing cam for indexing the platens between successive work stations.

Conveniently, the guide track which governs the path of the platens is circular and the bed is of annular form around a fixed central column which carries the tool heads, each segment of the bed spanning a work station. The circle may, however, be modified by insertion of straight sections.

One example of an automatic rotary transfer machine in accordance with the invention will now be described with reference to the accompanying drawings, in which:

FIGURES 1 and 2 are elevations seen at right angles to each other;

FIGURE 3 is a plan view of FIGURE 2;

FIGURE 4 is a fragmentary plan view of the machine bed spanning one work station;

FIGURE 5 is a sectional elevation of an inner platen clamp and the clamp operating mechanism on the line VV of FIGURE 4-,

FIGURE 6 is a fragmentary sectional elevation of an outer platen clamp on the line VI-VI of FIGURE 4;

FIGURE 7 is a part-sectional elevation on the line VII-VII of FIGURE 4 of a platen locating plunger;

FIGURE 8 is a plan view of a platen showing its connections to adjacent platens;

FIGURE 9 is a fragmentary section on the line IX-IX of FIGURE 8;

FIGURE 10 is a plan view of the platen advancing cam in its zero position, and

FIGURE 11 is a developed diagram of the cam track.

As seen best in FIGURES 1-3, the machine illustrated has a central rigid tool column 10 embraced by a generally annular machine base structure 11. The column shown is hexagonal, and carries four tool heads 12, each mounted on a respective fiat face of the hexagon. The base 11 carries six bed segments 11a11f (FIG. 3), each segment being symmetrical with a respective fiat face of the column 10 and spanning a single work station. FIG- URE 3 shows tool heads 12 at each of the four work stations defined by the bed segments 11b-11f, the work station at 11a being a loading and unloading station and the tool head at the station at 11f being omitted for purposes of illustration.

Six work-carrying platens 13 (only two are shown, broken away, in FIG. 3) are mounted concentrically on the bed 11a 11 and are interconnected, in a manner to be more fully described below with particular reference to FIGURES 8 and 9, so as to form a continuous annular work-table assembly, all the platens being indexed in synchronism on a curvilinear path through each work station in turn. The interconnection between platens has provision for small relative radial and circumferential movements to permit of the accurate location of each platen beneath a respective tool head. Location at each work station except the loading and unloading station is effected by hydraulically actuated plungers 14 (see also FIGURE 7), of which two only are indicated in FIGURE 3. After the locating action of the plungers 14 has been completed, inner and outer clamps 15, 16 engage the lower inclined flanges of inner and outer peripheral clamping channels 17, 18 in the edges of the platens 13 (only the outer clamping channel 18 is visible in FIGS. 1 and 2). The clamps hold the platens down firmly on the top face of the bed 11a and are 3 hydraulically actuated, as will be described below with particular reference to FIGURES 4, 5 and 6.

Each bed segment 11a is of generally hollow box-like construction, and within the base structure 11 is mounted a sloping chute 19 for swarf and spent coolant which registers at its lowest point with a swarf discharge conveyor 20 (see FIGS. 1-3).

Referring more particularly to FIGURE 4 of the drawings, each bed segment 11a, 11b is arcuate in plan, and the segments are bolted at 9 to the machine base 11, a shim 21 being optionally inserted in each radial joint to take up any inequalities in the mating faces of the segments.

Each bed segment has on its top surface an arcuate guide track or groove 22. The top surface of each segment at its junction with an adjacent segment has a pair of shallow 90 sector-shaped recesses each opening along one radius through the respective side wall of the guide track or groove 22, mating pairs of such recesses accommodating a semi-circular bridging plate 23. The diametral edge of each plate 23 initially projects slightly into the groove 22 so as to be machined by a finishing cutter which traverses the grooves 22 after assembly of the bed segments 11a so as to ensure accurate concentricity of the groove walls and a smooth continuous surface along the inward edge of each bridging plate across each junction between segments. Each bridging plate 23 is located on one bed segment by means of a dowel 24 and on the other segment by a screw 25 which is a slack fit in an oversize hole. This allows the necessary tolerance when assembling the plates.

The top surface of each segment 11a is also provided with a number of shallow rectangular air pockets 26. Into each pocket 26 opens a constricted orifice 27 communicating with an air distribution duct 28 fed with air under pressure from a common source (not shown).

Each bed segment 11b 11 also carries inner and outer clamps 15, 16 (see also FIGURES 5 and 6) which are actuated by means of hydraulic clamp and unclamp cylinders 30, 31 respectively which are mounted on opposite sides at the centre of a compensating bar 32. This bar floats freely in apertures in internal stiffening webs 33 in the bed segment. The ram 3-4 of the clamp cylinder bears against the inner end of a tubular thrust rod 35 which is supported in an outer bearing bush 36 located in an arcuate stiffening rib 37 of the bed segment 11b and an inner bearing bush 38 carried in a bracket 39. This bracket is located on the inner vertical wall 40 by means of a dowel 41 and clamped thereto by means of bolts 42 passing through the internal stiffening rib 37. The bracket 39 also carries the pivot pin 43 of the inner clamp 15.

Each end of the floating compensating bar 32 bears against a short tubular stub '44 (see FIGURE 6) which is slidable in a bracket 45 bolted on the outer face of the bed segment 11b and carrying the pivot 46 of one of the outer clamps 16. Thus, when hydraulic fluid under pressure is admitted to the clamping cylinder 30 through the pipe connection 47, the ram 34 pushes the tubular thrust rod 35 inwards against the reaction of the compensating bar 32, which reaction force is transmitted thereby equally to the short tubular stub 44 at each end, so that the bottom ends of the inner and outer clamps 15, 16 all experience equal forces which tend to turn them on their respective pivot pins 43, 46 in the direction for forcing their upper inturned end into contact with respective bearing blocks 48 on a platen 13 (see also FIGURE 8). The coacting faces of the clamps 15, 16 carry replaceable pressure pads 49.

The unclamping cylinder 31 is fixed to the compensating bar 32 coaxially with the clamping cylinder 30 and its ram 50 is secured at its inner end to an unclamping rod 51 which is free to slide within the tubular clamping rod 35 and the ram 34 of the clamping cylinder 30. At its free end the rod 51 passes through a clearance hole 52 in the tail of the inner clamp 15. The projecting tip of the rod 51 is grooved at 53 to engage a tongue 54 on the clamp 15, part of the tip which forms a side wall of the groove 53 being machined away at 55 so that, by rotating the rod 51, it can be disengaged from or engaged with the tongue 54 to facilitate dismantling or assembly, as the case may be.

At its outer end, the ram 50' is slidable in a bush 56 carried by .a bridge piece 57 on the outer edge of the bed segment 11]) An adjustable stop sleeve 58 is clamped on this outer end of the ram '50 to limit its freedom of outward travel by contact with the bridge piece 57.

When the unclamp cylinder 31 is supplied with pressure fluid through the pipe union 59, the ram 50 moves in the direction for bringing the adjustable stop 58 into contact with the bridge piece 57, and at the same time pulls the unclamping rod 51. The latter, through the interengagement of the groove 53 and the tongue 54, rocks the inner clamp 15 in the direction for lifting the pad 49 from the bearing block 48.

When the stop 58 makes contact with the bridge piece 57, the thrust reaction against the cylinder 31 forces the compensating bar 32 inwards. As shown in FIGURE 6, each end of this bar is locked by a cotter pin 60 to a short pull rod 61 which slides freely within the thrust tube 44 and the tail of the respective outer clamp 16, its projecting end carrying an adjusting nut 62. Hence inward movement of the bar 32 pulls the tails of the outer clamps 16 in the direction for rocking the pad 49 on the respective clamp out of contact with its bearing block 48 on the platen 13. The latter is thus released from its grip on the bed segment 11b Referring also to FIGURE 7, each bed segment 11b carries a pair of platen-locating plungers 14 adjacent each front or outer corner. Each plunger 14 slides on a linear ball bearing 64 in a sleeve 65 locked in the segment 11b The plunger 14 is movable between a lower or retracted position in which its tip is flush with, or lies just below, the top surface of the bed segment, and a raised or locking position in which the plunger enters a corresponding and accurately machined socket 66 in the platen (see FIG. 8). This reciprocatory displacement is effected by an hydraulic motor 67 bolted to the underside of the bed segment.

The lower end of the plunger 14 has a pair of axially spaced abutment rings 68, 69 between which lies a trip lever 70. This lever operates a limit switch 71 which serves to signal completion of the strokes of the plunger to the mechanism for controlling tool feeds and platen advance.

FIGURES 8 and 9 illustrate the construction of a platen 13. Each platen is of generally similar shape and size, when seen in plan, to that of a bed segment 11a 11f-that is to say, it forms a segment of a circle extending from the point A to the point B on its outer perimeter, as shown in FIGURE 8. All the platens 13 form a continuous movable table supported on the bed segments 11a 11 and are interconnected in push-pull at adjacent ends by bolts 73. The bolts pass through clearance slots 74 in vertical end webs or walls 75 and through the limbs of U-shaped brackets 76 which are dowelled and bolted to the respective adjacent platens 13. Compression springs 173, 174 are placed on each bolt 73 between the head or the nut and the respective adjacent bracket 76, these springs being stiff enough to remain undeflected under normal indexing loads but capable of yielding as required when the locating plungers 14 are operated.

At each end, each platen 13 is stepped at 77 and 78, the step 77 being relatively shallow and running from the front to the back edges of the top of the platen in a direction parallel to the central radius through the segment. The step 78 is deeper and is continued into the end walls or webs 75. The shallow step or recess 77 accom modates a relatively thin cover plate 79 (omitted from the left-hand end of FIGURE 8) which serves to preserve the continuity of the top faces of the platens and provides a swarf guard to keep swarf away from the gap between platens.

On the lower step 78 rests a connecting plate 80 bolted to the lower step 78 by bolts 81 which pass with clearance through corresponding holes 82 in the connecting plate 80. The top ends of the bolts 81 are counterbored and threaded to receive set screws 83 which hold the cover plate 79 in place. All the fixings at 73, 81, 83 allow for a limited amount of relative radial and peripheral motion between adjacent platens when the locating plungers 14 engage in their respective sockets 66.

On its underside, each platen 13 carries three equiangularly spaced sets of rollers which engage the guide track or groove 22 in the bed segments 11a The outer end sets each comprises two coaxial rollers 85, 86 mounted on a common stub shaft 87 which is locked in the platen, The upper roller 85 of each of these sets runs in the groove 22 whilst the lower roller 86 engages in an advancing cam groove as described below with reference to FIGURES and 11. The centre roller set consists of a single (upper) roller 88 mounted on a peg 89 with its axis 90 slightly offset from the axis 91 of the peg. An integral flange 92 on the peg engages the bottom of a. shallow recess 93 in the under surface of the platen, and its upper end is keyed to an indexing plate 94 having diametrically opposed 90 arcuate slots 95 through which pass clamp screws 96. A nut 97 tightens the peg 89 in the adjusted position. The indexing plate 94 and associated parts are housed in a recess 98 in the top face of the platen 13.

The arrangement of rollers 85, 86, 88 is such that, when the platen 13 is placed on a bed segment 11a with the upper rollers 85, 88 engaged in the guide track 22, the central roller assembly is adjusted by rotating the indexing plate 94 until the roller 88 bears against a side wall of the groove 22 with sufficient pressure to force the upper rollers 85 into contact with the other side wall of the track 22 until there is normally a suitable minimum of float of the platen 13 in the radial direction on the bed segment 11a This adjustment is preferably made after all the bed segments 11a 113 have been assembled on the base structure 11 and the entire guide track groove 22 has been finish machined to ensure accuracy of concentricity and smoothness of transition from segment to segment. It is preferably also effected when the platen 13 concerned is not fully indexed to its working position, the walls of the groove 22 being relieved or recessed slightly where they are normally engaged by the upper rollers 85, 88 so as to impart to the platen 13 a sufiicient degree of radial float to ensure freedom of radial displacement when the locating plungers 14 fully enter their respective sockets 66. Thus, final locating of the platen 13 at any one work station is not affected by the engagement of the follower rollers 85, 86, 88 with the sides of the groove 22.

The top face of the platen 13 has four large cavities 98 bounded by lands 99 which are machined flat to carry work-holding jigs or fixtures (not shown) for clamping the work.

Each lower roller 86 on an end stub 87 is engageable with a cam track 100 (see FIGURES 10 and 11) the positions of the upper and lower boundaries of which are indicated by chain lines in FIGURE 9. This track is a groove machined in a generally cylindrical spool 101 mounted in bearings (not shown) in the bed segment 11a. The successive positions of one of the lower rollers 86 on a platen 13 are shown in FIGURES 10 and 11 at 86a, 86b and 860. Short dwell periods are allowed at each end of the track 100 by run-in and run-out circumferential sections 102, 103 respectively of the track, and these allow the smooth pick-up of the succeeding roller 86 on a platen when the preceding roller has completed its traverse of the sinuous part of the cam track. In the arrangement illustrated, the cam spool 101 must complete two revolutions 6 to traverse a platen 13 through one indexing displacement. As shown in FIGURE 10, the rollers 86 move in an arcuate path 104 in the direction of the arrowheads I for a direction of rotation R of the spool 101. The revolutions of the cam spool are controlled by a conventional stop mechanism (not shown).

In operation of the machine, work is loaded onto an empty platen 13 at the station spanned by the bed segment 11a in FIGURE 3. At the succeeding stations 11b 11f it is machined by the tool heads 12 and then unloaded at station 11a. At each machining station 11b 11 the tool heads 12 are gauged by reference to the locating plungers 14, so that when a platen 13 is indexed by the earn into a working position, the plungers 14 at that station accurately locate the work both radially and circumferentially, the relative play permitted between adjacent platens by the interconnecting elements 73, 81 being sufiicient for this purpose. Consequently, errors in the initial gauging and clamping of the work are not cumulative as it progresses through its several work stations.

The sequence of operations of the plungers 14, clamps 15, 16, and cam spool 101 are phased by a controller of conventional design. Thus, when all the tool heads 12 at the several work stations have completed their operations and have all been retracted from engagement with the work, a valve in the hydraulic circuit of each plunger actuating cylinder 67 is moved to cause the plungers to retract. Simultaneously, or immediately thereafter, the unclamp cylinder 31 is energised to release the inner and outer clamps 15, 16. The motor driving the cam spool 101 is then energised to rotate the spool. At the same time, an air valve in the compressed air circuit to the ducts 28 is opened to raise the air pressure in the pockets 26 in all the bed segments 11a 11 so that the weight of each platen 13 is at least partly taken off the top surfaces of the bed segments to relieve friction during indexing of the platens 13.

The cam track 100 exactly spans the arcuate pitch of the lower rollers 86, which is nominally constant both for all platens and between platens. The cam spool 101 is set to stop with a roller 86 resting in each dwell section 102, 103, thus ensuring that the platens 13 are always brought to rest in a position of approximate registration of their sockets 66 with the respective plungers 14.

As shown in FIGURES l3, the base structure 11which is normally fabricated-can be optionally provided with seatings 105 against which outrigger pedestals (not shown) can be registered to carry additional tool heads for machining the work on the radially outward side.

The foregoing description of a transfer machine having a segmented bed structure is illustrative of the invention and reveals the simplification which is thereby introduced into the problem of access for servicing the mechanisms involved in indexing and locating the work. Furthermore, any excessive localized wear in a component of the bed and platen assembly can be easily, and economically effected by removing the affected platen or bed segment and replacing it with a sound component, thus minimizing the shut-down period of the machine. A number of relatively small standardized components can be stocked for the purposes of replacement, and the actual cost of repairing and servicing the machine is correspondingly reduced. An elaborately equipped repair shop is thus rendered unnecessary, reducing both capital and labour charges and freeing factory space for productive purposes.

By the omission of the central guide rollers 88, the platens 13 can be traversed over a straight section of guide track 22 should the interposition of such a section between any two adjacent bed segments be found necessary or desirable. In such an arrangement, the method of interconnection of the platens 13 would be modified to take account of the relative angular motion when passing from a curved to a straight path and vice versa.

A further advantage arising from the segmental construction of the bed is that the central column can be of 7 larger section than usual, and more rigidly mounted than is possible with conventional machines.

Although the particular machine described and illustrated has six stations, including one loading station, modifications are envisaged in which a different number of stations are provided, the form of the central column and the number of bed segments being modified accordingly. In'some cases, also, it may be convenient to provide some bed segments 11a whose mean length, in the direction of indexing travel of the platens 13, is equal to the span of two or more work stations. It is preferred, however, that each bed segment should be of a mean length to exactly span a whole number of work stations.

I claim:

1. A transfer machine comprising a base structure; a bed structure mounted thereon and having a platen-supporting surface which defines a continuous curvilinear path; a plurality of work stations disposed at predetermined intervals on said curvilinear path; a plurality of similar Work-carrying platens supported on said bed structure and occupying the full extent of said curvilinear path; a common indexing mechanism in one of said bed segments for indexing all the platens simultaneously past successive work stations; means on each platen for engaging said indexing mechanism; and a push-pull interconnection between each pair of adjacent platens for transmitting the indexing motion to all platens simultaneously.

2. A transfer machine according to claim 1 wherein the continuous curvilinear path is circular and each work station occupies a sector of said path of equal angular extent to that of every other Work station.

3. A transfer machine according to claim 2 wherein a central column is located within the ambit of the curvilinear path and is adapted to carry a tool head at any desired work station, and the bed structure is constituted by separate segments each spanning a work station and detachably secured to the base structure.

4. A transfer machine according to claim 1 wherein the platen-supporting surface has a guide groove opening therethrough and each platen has a follower projecting thereinto, and the common indexing mechanism is a cam whose cam track registers with the bottom of said groove for engagement by successive platen followers.

5. A transfer machine according to claim 1 wherein the bed structure is composed of separate bed segments each having an arcuate guide track formed on the platen-supporting surface thereon and adapted to register with each adjacent guide track for engagement by coacting rollers on each platen, the working face of the guide track being relieved by a small amount at the points where it is engaged by the rollers of a platen correctly located at a station so as to permit such radial play between the platen and the guide track as is necessary to ensure accurate radial location of the platen relative to a tool head.

6. A transfer machine according to claim 1 wherein the platen supporting surface is formed with a plurality of shallow pockets distributed over the area of each work station, each pocket having a constricted orifice opening thereinto, and air pressure distributionducts interconnect all said orifices; and wherein releasable clamping means is provided for holding a platen tightly onto the platen supporting surface at each Work station.

7. A transfer machine according to claim 6 wherein the clamping means comprises a plurality of clamps disposed adjacent a side edge of the platen supporting surface at a work station; a first hydraulic cylinder for applying all said clamps and a second hydraulic cylinder for releasing all said clamps; and a floating compensating bar carrying said cylinders and mechanically coupled to at least all but one of said clamps.

8. A transfer machine having a base structure providing a plurality of work stations; tool heads located in at least some of said work stations; a plurality of separate bed segments each detachably secured on said base structure to form a supporting surface extending in a closed path through all said work stations; a plurality of workcarrying platens slidably supported on said bed segments and occupying the full extent thereof; interconnections between all said platens affording limited freedom of individual relative locating displacement of each platen with respect to each successive tool head; and means for in: dexing all said platens simultaneously, each bed segment having a plurality of shallow pockets distributed over its platen-supporting surface; a constricted orifice opening into each pocket; air pressure distribution ducts interconnecting all said orifices, and releasable clamping means for holding a platen tightly onto the platen-supporting surface of the bed segment, said clamping means comprising a plurality of clamps disposed on opposite side edges of a bed segment; a first hydraulic cylinder for applying all said clamps and a second hydraulic cylinder for releasing all said clamps; and a floating compensating bar carrying said cylinders and mechanically coupled to at least all but one of said clamps.

9. A transfer machine having a base structure providing a plurality of work stations; tool heads located in at least some of said work stations; a plurality of separate bed segments each detachably secured on said base structure to form a supporting surface extending in a closed path through all said work stations; a plurality of workcarrying platens slidably supported on said bed segments and occupying the full extent thereof; interconnections between all said platens affording limited freedom of individual relative locating displacement of each platen with respect to each successive tool head; and means for indexing all said platens simultaneously, the interconnection between a pair of adjacent platens comprising an abutment on each platen; a tension member resiliently engageable with each abutment; a connecting plate adapted to overlie the gap between the adjacent ends of the platens, and securing bolts passing through oversize holes in the plate to permit limited freedom of relative radial and peripheral movement between the platens to accommodate the locating displacements of the individual platens relative to each tool head.

References Cited UNITED STATES PATENTS 2,852,960 9/1958 Brems 7482l 2,857,787 10/1958 Natalis 7482l 2,903,120 9/1959 Thomas 19819 3,209,623 10/1965 Schardt. 3,277,696 10/1966 Gertel.

EDWARD A. SROKA, Primary Examiner.

US. Cl. X.R. 198181, 209; 269-57 

